1. Field of the Invention
The present invention relates to a multi-purpose microwave oven, and more particularly, to an air duct in a multi-purpose microwave oven in which an oven lamp is provided in an air duct and cooled by flow air passing through the air duct so as not to be overheated by self-heat and external heat.
2. Discussion of the Related Art
Generally, a microwave oven is a cooking machine which cooks food by friction heat between molecules as arrangement of molecules is deranged using high frequency of about 2,450 MHz as a heat source. Particularly, a multi-purpose microwave oven has a convection function and a combination function as well as a microwave function. The convection function is performed in such a manner that food is cooked at hot air by heat of a heater. The combination function combines the microwave function with the convection function.
The multi-purpose microwave oven will be described with reference to FIGS. 1 and 2.
As shown in FIGS. 1 and 2, the multi-purpose microwave oven includes a main body 1, a base plate 2 on which the main body 1 is mounted, a U-bended outer case 3 which covers an upper part and both sides of the main body 1, a door 4 and a control panel 5. The door 4 and the control panel 5 are mounted at the front of the main body 1.
A cooking chamber 10 is provided at one side inside the main body 1, and a component chamber 11 is provided at the other side inside the main body 1. Various components required to drive the microwave oven are collected in the component chamber 11.
Furthermore, a tray 12 is provided on the bottom inside the cooking chamber 10 and rotated by a motor (not shown) to evenly heat food put on the tray. A heater 13 is provided on an upper part outside the cooking chamber 10. The heater 13 emits heat when the convection function is operated so that the heat of the heater 13 flows into the cooking chamber 10 through a porous part 10a which is formed on a top surface of the cooking chamber 10.
Main components such as a transformer 21 and a magnetron 20 which is a high frequency oscillator are provided in the component chamber 21. The transformer 21 transforms power source for home use to high voltage required to oscillate the magnetron 20. Furthermore, a cooling pan 22, a waveguide 23, and an air duct 24 are provided in the component chamber 21. The cooling pan 22 includes a pan motor for cooling high heat generated when oscillating the magnetron 20. The waveguide 23 guides microwave generated by the magnetron to the cooking chamber 10. The air duct 24 guides air generated by rotative force of the cooling pan to the cooking chamber 10.
In the aforementioned multi-purpose microwave oven, to heat/cook food, in a state that the cooking chamber 10 is opened by opening the door 4, cooking food is put on the tray 12 and then the door 4 is closed to seal the cooking chamber 10.
Subsequently, one of the microwave function, the convection function and the combination function is selected in accordance with food type and food state, so that the microwave oven is operated.
For example, if the microwave function is selected, high frequency of about 2,450 MHz per second is oscillated from the magnetron 20 and propagated into the cooking chamber 10 through the waveguide 23. The high frequency propagated into the sealed cooking chamber 10 is scattered and reflected on the wall of the cooking chamber 10 to be incident upon the food. Thus, arrangement of molecules of the food is deranged. For this reason, friction heat between the molecules is generated so that the food is heated and cooked.
If the convection function is selected, the heater 13 emits heat and the heat of the heater 13 flows into the cooking chamber 10 through the porous part 10a. Thus, the food is heated by the convection. In this case, to preserve a temperature in the cooking chamber, the air duct 24 is closed so as not to flow air generated by the cooling pan 22 from the component chamber 11 into the cooking chamber 10. To this end, a damper 26 is provided in the air duct 24 and is controlled by a solenoid 25.
Meanwhile, a porous part 14a is formed in a partition 14 which isolates the cooking chamber 10 from the component chamber 11. An oven lamp 27 is formed at a side of the component chamber 11 next to the porous part 14a so as to illuminate the cooking chamber 10 through the porous part 14a.
Particularly, to improve illuminance, the oven lamp 27 is mounted in a stainless lamp box 28 having excellent reflexibility. A heat blocking plate 29 is provided at a side of the lamp box 28 to block cooking heat generated during cooking (see FIG. 2).
However, as heat emitted from the oven lamp 27 is combined with cooking heat, heat of about 200.degree. C. is actually conducted to the heat blocking plate 29. As a result, the heat blocking plate 29 has poor heat blocking function. This often shorts the oven lamp 27, reduces its service life, and incurs the A/S cost.
Furthermore, since the air duct 24 is separated from the oven lamp 27, the volume of the microwave oven increases and the number of components increases, thereby causing adverse effect in price competition.